1. Field of the Invention
The present invention relates to the continuous casting of metal, and more particularly, to a mandrel for use in the continuous casting of hollow ingots.
The invention is particularly applicable to continuous casting of hollow ingots of from 270 to 750 mm in outside diameter and from 100 to 350 mm in inside diameter. Additionally, the invention is readily applicable to the continuous casting of hollow ingots from carbon and alloy steels of larger diameter.
2. Background
In modern practice there is a strong trend towards utilization of mandrels made in the form of hollow rods for use in the continuous casting of hollow ingots.
It has been observed that metal penetration into the interior of the hollow ingot being cast is possible in the process of casting. Therefore, temperature transducers are mounted on inlet and outlet pipes through which passes water for cooling a mandrel, whereby the water temperature gradient is controlled throughout the casting process. Shortly after the beginning of the ingot withdrawal cycle, the temperature gradient increases to a prescribed value which depends upon the mandrel construction, consumption of the coolant used and on various other factors. An increase in the temperature gradient of the cooling water above the prescribed level indicates rupture of the ingot crust formed on the mandrel; this being a signal to discontinue the withdrawal operation.
It has been found in the course of continuous casting of steel hollow ingots, that the control method mentioned above makes it possible to reliably detect the rupture of the ingot internal crust and to minimize occurrences of metal penetration into the ingot interior. On the other hand, the termination of the withdrawal operation results in the adherence of the ingot internal crust to the mandrel surface, whereby bridging is formed thereon.
To avoid the bridging phenomenon, the mandrel is formed with openings for the passage of gases to cut through the ingot crust which envelops the mandrel. Though such construction permits the ingot crust to be removed from the mandrel, it still fails to allow the casting process to be resumed.